1. Field of the Invention
The present invention relates to the conveyance of pulverized materials and more specifically to a pressurized conveyor capable of transporting pulverized coal to a higher pressure zone.
2. Description of the Prior Art
The practice of feeding pulverized coal into a coal gasifier presents a difficult problem. Owing to the fact that a gasifier operates at an elevated pressure level whereas the coal is generally stored at atmospheric pressure, a reliable economic conveyor is necessary to transcend the large pressure differential involved so that the coal may be fed into the gasifier.
The prior practice has been to use various expensive and complicated conveying systems, e.g., lock hoppers and pumped slurry systems. At highly elevated pressures, i.e., 1500 psi, it is believed that the valves currently employed in lock hopper systems may not be reliable. In addition, the gas compression cost becomes prohibitive as the pressure differential increases. Slurry pump systems have also proved to be expensive. Not only does the pulverized coal have to be slurried, but, prior to its introduction into the gasifier, it must be deslurried through an involved series of steps involving various heaters, settling tanks and pumps. Furthermore, if a water slurry is employed, any water injected into the gasifier will depress the flame temperature thereby necessitating elaborate dewatering systems. An oil slurry is unattractive because of the cost of oil.